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<h1 id="array-creation">Array creation</h1>

<p>Before we do some fancy numeric stuff or even machine learning we have to clear one thing.</p>
<p><strong>How do we generate NDArrays?</strong></p>
<p>Since NDArray is the key class in SciSharp stack there must be numerous possibilities how to generate this arrays. And yes that’s the case.</p>
<p>Maybe first of all we should see the dump way – which can be always used but is not too user friendly.</p>
<p><strong>Dump way</strong></p>
<pre><code class="lang-CSHARP">// first standard constructor
// you also specify the generic type of the NDArray
var np = new NDArray&lt;double&gt;();

// set 9 elements into this array
np.Data = new double[] {1,2,3,4,5,6,7,8,9};

// shape it to a 3x3 matrix 
np.Shape = new Shape(3,3);
</code></pre>
<p>Ok looks not too difficult. But also not too userfriendly.</p>
<p>We create an empty NDArray&lt; double &gt;, fill it with 9 elements and shape it to 3x3 matrix.</p>
<p>At this point we could shape it also to a 1x9 vector but we shaped it to a 3x3.</p>
<p>So with this 3x3 shaped NDArray we can do matrix multiplication but with a 1x9 we could not.</p>
<p>Always be careful with your shape and be sure what you want to do with your elements.</p>
<p><strong>Create by enumeration</strong></p>
<pre><code class="lang-CSHARP">// at this point we use a numpy class so it looks like numpy function call 
var np = new Numpy&lt;double&gt;();

// we take the Data / elements from an array 
// we do not need to define the shape here
var np1 = np.array(new double[] {1,2,3,4,5,6} );
</code></pre>
<p>Ok as we can see, this time the array was created without define the shape.</p>
<p>This is possible since the method expect that the double[] array shall be transformed into a NDArray directly.</p>
<p><strong>Create by given range</strong></p>
<pre><code class="lang-CSHARP">var np = new Numpy&lt;double&gt;();

// we simple say &quot;create an array with 10 elements&quot;
// start is expected to be 0 and step 1
var np1 = np.arange(10);

// this time start with 1, step 2 
// and do it as long as smaller than 10
var np2 = np.arange(1,10,2);
</code></pre>
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